Evaluation of the cellular and molecular mechanisms mediating peptide hormone secretion constitutes an important component of our research efforts. The close interrelationships mediating neuroendocrine responses within the hypothalamic-pituitary- gonadal/adrenal system offer an excellent opportunity to analyze some unique characteristics of peptide-peptide, peptide-amine, and peptide-amine-steroid interactions. Studies using pituitary cell cultures were directed to evaluate the precise mechanisms through which different peptidergic or aminergic secretagogues enhance or suppress peptide hormone release. A main target of our research efforts has been to analyze the role of hormonal input signal in modifying cellular responses, using a computerized perfusion system that can exquisitely regulate the delivery of appropriately- designed hormone signals to cells or tissues (in vitro). Additional studies were conducted to evaluate characteristics of hormone-receptor interactions (post-receptor as well as transmembrane events involved in the hormone-release process) and to define the specific intracellular messengers transducing the action of key hypothalamic peptides involved in pituitary hormone release. A major part of this project included work directed to understand the role of pulsatile hormone secretion in providing coded messages for the activation of endocrine target tissues. Several experiments were conducted to analyze the pulsatile secretion pattern of different peptide hormones (LHRH, LH, ACTH, Prolactin) that are intimately involved in the regulation of endocrine and reproductive functions. The characteristic pattern of secretion of each hormone was defined as well as the role of certain neural or gonadal factors in modulating the pulsatile pattern. Qualitative differences in pulsatile peptide secretion were uncovered. The information obtained provides a clearer understanding of the mechanisms regulating episodic hormone secretion.